Method and apparatus for removing organic films

ABSTRACT

A method and an apparatus for removing an organic film such as a resist film from a substrate surface are provided. These are very safe even at high temperatures, and use a treatment liquid which can be recycled and reused. A treatment liquid typically formed from liquid ethylene carbonate, propylene carbonate, or a liquid mixture of these two compounds, and in particular such a treatment liquid containing dissolved ozone, is contacted with a substrate with an organic film, and the organic film is removed. Furthermore, an apparatus of the present invention (A) a treatment liquid delivery device for transporting the treatment liquid to a treatment area, (B) a film contact device for bringing the treatment liquid into contacting with the organic film surface of the substrate within the treatment area, (C) a liquid circulation device for recycling treatment liquid discharged from the treatment area and returning the recycled liquid to the treatment area via one or more temporary storage devices, and (D) an ozone dissolution device for bringing ozone containing gas into contact with the treatment liquid either within the treatment area and/or within the temporary storage devices.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of removing an organicfilm adhered to a substrate, enabling the surface of an electronicdevice substrate or the like to be cleaned, and also relates to anorganic film removal apparatus and a resist film removal reagent. Inparticular the invention relates to the removal of photoresist filmsused during the processing of semiconductor wafers or liquid crystalsubstrates. Furthermore, the invention also relates to the removal oforganic contaminant films or fine particles from such substrates. Inaddition, the present invention can also be applied to the removal ofmore typical organic films such as oil films or paint films from asubstrate.

[0003] 2. Description of the Prior Art

[0004] The removal of photoresists used during the ultra fine processingof oxide films or polysilicon films typically employs a method whereinthe substrate is immersed in a mixed solution of sulfuric acid (3 or 4parts by volume) and hydrogen peroxide (1 part by volume) (known aspiranha) and heated at 110 to 140° C. for 10 to 20 minutes. In thosecases in which a high concentration ion implantation has been performedusing a resist mask, the resist itself degenerates and cannot be easilyremoved using a piranha solution, and consequently ashing with plasmaexcited oxygen is typically employed. Resists which have sufferedsurface degeneration following dry etching are also removed in thismanner. However, if an entire photoresist is subjected to ashing,organic decomposition residues, fine particles and minute quantities ofmetal derived from the resist remain, and films of decomposed materialalso remain on the side walls of channels which have undergoneprocessing. In addition, because the ashing process requires a highenergy plasma, the surface of the wafer is also exposed to damage whichcould harm a semiconductor device. Consequently, ashing is typicallyperformed so that a minute quantity of the resist film remains, and thisresidual resist is subsequently removed using either piranha treatment,or treatment with an organic solvent such as n-methylpyrolidone (NMP),dimethylsulfoxide (DMSO) or an amine in the case of a metal wiring filmprocess.

[0005] Piranha treatment discharges large quantities of sulfuric acid,and similarly treatments which use organic solvents also consume largequantities of solvent, and consequently both types of treatment causelarge environmental problems. As a result, resist removal using ozonewater has recently been tested. The solubility of ozone in waterincreases as the temperature is lowered, and if a gas containing a highconcentration of ozone (hereafter referred to as ozone gas) is used,then the solubility of ozone in cold water of approximately 0° C.reaches 70 to 100 ppm. However, with this type of ozone water treatment,the stripping rate for a novolak resin based positive resist film usedwith i-line radiation, which is a widely used configuration in LSIproduction, is slow, at not more than 0.1 μm/minute, meaning thetreatment is not entirely practical. Recently, methods involvingtreatment with a combination of a high concentration ozone gas and watervapor, and methods involving treatment with a high concentration ozonewater utilizing pressurized ozone have also been developed, but thestripping rates with these methods is still slow at approximately 1μm/minute, and in the case of a substrate comprising a metal wiring filmof Cu, W or Mo or the like, damage to the film also becomes a problem.

[0006] Regardless of whether piranha treatment or organic solventtreatment is used, from a productivity perspective, the process involvesthe treatment of a plurality of wafer containing carriers which areinserted in a liquid contained within a cleaning vessel. In the formertreatment, hydrogen peroxide decomposes forming water, and the solutiongradually becomes diluted, requiring the addition of more hydrogenperoxide, although there is a limit to the amount of additional hydrogenperoxide that can be added. Accordingly, the usable lifespan of thechemical solution in the cleaning vessel is surprisingly short, andlarge volumes of sulfuric acid need to be discharged, resulting inconsiderable costs associated with environmental measures. In the caseof the latter treatment, repeated use results in an accumulation ofdissolved resist within the solvent, which leads to an increase inreverse contamination of the wafer and places a larger load on the rinsesolution. Accordingly, the solvent within the cleaning vessel needs tobe changed quite regularly. Certainly, neither treatment can be claimedto be economical.

[0007] Resists which have undergone strong dry etching or highconcentration ion implantation and have suffered considerabledegeneration are impossible to remove using conventional wet treatments,and these types of resists are currently removed using ashing methods.However as described above, ashing has a considerable number ofassociated problems, and also requires a subsequent wet treatment.

[0008] In a wet treatment using an organic solvent, metal impuritieswithin the resist migrate into the treatment liquid, and as thetreatment liquid is used repeatedly the concentration within the liquidof metal derived from the resist increases. If this metal is a metalwith a larger oxide formation enthalpy than silicon, such as iron, zincor aluminum, then there is a danger of substitution via Si—O linkagesoccurring at the resist removal surface, resulting in contamination ofthe surface.

[0009] Furthermore, resist removal using organic solvents is used almostexclusively in cases in which the substrate is a metal wiring film.Removal solvents with a strong stripping performance typically containan amine, and if a rinse with pure water is performed immediately aftertreatment then strongly alkaline sections are generated, and there is aconsiderable danger of damage being caused to the metal film of thesubstrate. Accordingly, the treatment solvent is exchanged withisopropyl alcohol prior to rinsing with pure water, making increases inthe organic solvent consumption unavoidable.

[0010] A photoresist stripping liquid composition formed from4-methoxy-1-butanol, 3-methoxy-1-butanol or a mixture of4-methoxy-1-butanol and 3-methoxy-1-butanol, together with propylenecarbonate is disclosed in Japanese Patent Publication No. 2679618 (JP2679618 B), although no mention is made of the use of only propylenecarbonate, and similarly no mention is made of ozone use.

[0011] Furthermore, U.S. Pat. No. 5,690,747 discloses a method forremoving a photoresist in an ultrasonically agitated solvent comprising(a) 40 to 50 vol % of an aprotic cyclic carbonate ester such as ethylenecarbonate, (b) an aprotic polar compound such as ethylene diacetate andethylene dibutyrate, as well as the solvents N-methyl-2-pyrrolidone andtriethanolamine. In addition, the cleaning effect of ethylene carbonateand propylene carbonate on ink and the like has also been reported.However, there have been no reports regarding the use of only ethylenecarbonate or propylene carbonate for photoresist removal, nor on theircombined use with ozone.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide a method and anapparatus for effectively removing not only resists, but also otherorganic films such as oil films and paint films, which are capable ofachieving an extremely rapid stripping rate of 20 μm/minute for atypical resist film, and are also capable of removing even resist filmswhich have undergone considerable degeneration as a result of ionimplantation or the like at a satisfactorily productive stripping rateof several ttm/min, and which moreover do not damage the surface of thesubstrate beneath the film, do not suffer from the types ofenvironmental problems described above, and are extremely economical.

[0013] A first aspect of the present invention provides a method forremoving an organic film on a surface of a substrate, comprising:

[0014] bringing a treatment liquid comprising liquid ethylene carbonate,propylene carbonate, or both of them into contact with said substrate toremove said organic film, thereby allowing material constituting saidorganic film to migrate into said treatment liquid,

[0015] decomposing said material in said treatment liquid into lowmolecular weight material by ozone, thereby said ozone treated treatmentliquid being regenerated as a treatment liquid, and

[0016] recycling the treatment liquid thus regenerated for treatinganother substrate.

[0017] A second aspect of the present invention provides a method forremoving an organic film on a surface of a substrate, comprising:

[0018] bringing a treatment liquid containing ozone dissolved in aliquid comprising ethylene carbonate, propylene carbonate, or both ofthem into contact with said substrate with an organic film on a surfacethereof to remove said organic film, wherein said organic film isdissolved said treatment liquid and decomposed into low molecular weightmaterial, and

[0019] using the treatment liquid after removal of said organic film fortreating another substrate.

[0020] In a preferred embodiment of the second aspect of the presentinvention, said treatment liquid after removal of said organic film isrecycled as a treatment liquid as it is for treating another substrate.

[0021] In another preferred embodiment of the second aspect of thepresent invention, said treatment liquid after removal of said organicfilm is further subjected to treatment with ozone, and then recycled asa treatment liquid for treating another substrate.

[0022] A third aspect of the present invention provides an apparatus forremoving an organic film from a surface of a substrate comprising:

[0023] (A) a treatment liquid delivery means for transporting atreatment liquid comprising liquid ethylene carbonate, propylenecarbonate, or both thereof to a treatment area,

[0024] (B) a film contact means for bringing the treatment liquid intocontact with the surface of said organic film of the substrate withinthe treatment area,

[0025] (C) a treatment liquid circulation means for recycling treatmentliquid used and discharged from the treatment area back to saidtreatment area via one or more temporary storage means, and

[0026] (D) an ozone-containing gas contact means for bringing anozone-containing gas into contact with the treatment liquid dischargedfrom said treatment area within said treatment area and/or within atleast one of said temporary storage means.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a schematic longitudinal sectional view of an apparatusemploying the present invention in the immersion of a wafer requiringtreatment.

[0028]FIG. 2 is a schematic longitudinal sectional view of an apparatusemploying the present invention in a single wafer spin method.

[0029]FIG. 3 is a schematic longitudinal sectional view of an improvedchamber and ozone gas supply system for the apparatus of FIG. 2.

[0030]FIG. 4 is a schematic longitudinal sectional view of an improvedtreatment liquid supply system for the apparatus of FIG. 2.

[0031]FIG. 5 is a schematic diagram of a batch treatment apparatusemploying the present invention in the immersion of wafers requiringtreatment.

[0032]FIG. 6 is a schematic diagram of a treatment apparatus using amixed liquid of ethylene carbonate and propylene carbonate according tothe present invention and employing a batch immersion method.

[0033]FIG. 7 is an overhead view showing a trace of a nozzle during theback and forth movement of an oscillator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] As follows is a more detailed description of the presentinvention.

[0035] The major characteristic of the present invention is the use of apreviously untested ethylene carbonate and/or propylene carbonatetreatment using ozone, for the stripping and removal of resist films andthe like. (Hereafter, the term “alkylene carbonate” may be used todescribe “ethylene carbonate and/or propylene carbonate”. Similarly, theterm “alkylene carbonate treatment” may be used to describe “ethylenecarbonate and/or propylene carbonate treatment”).

[0036] [Treatment Liquid]

[0037] Ethylene carbonate (melting point 36.4° C., boiling point 238°C., flash point 160° C.) is readily soluble in water, and at roomtemperature is a comparatively stable colorless, odorless solid,although upon heating it becomes a liquid and can be used as an aprotic,polar solvent. The fact that the boiling point and the flash point arehigh, and the toxicity is low, together with the fact that it is notclassified as a hazardous material under the Fire Services Act, makesethylene carbonate a preferred solvent. Propylene carbonate (meltingpoint −48.8° C., boiling point 242° C., flash point 130° C. or higher)is a liquid at low temperatures, and with the exception of beingclassified as a type 4 hazardous material, is a solvent with similarproperties to ethylene carbonate.

[0038] These alkylene carbonate liquids have a powerful solvency actionwith respect to aromatic hydrocarbons, although the solubility parameter(SP value), derived from the molecular cohesive energy density, is largeat approximately 14. In theory, the closer the SP values match, thebetter the solubility becomes, and as the SP value of the polymers usedas resist materials are typically around 10, the use of strippingsolvents with similar SP values, such as NMP which has an SP value of11, has become widespread. However, the inventors of the presentinvention have discovered that alkylene carbonate liquid, by itself,when heated displays a similar or even superior stripping performance toconventional stripping solvents.

[0039] This alkylene carbonate liquid is a polar solvent, andconsequently the solubility of ozone is poor. However, even at lowconcentrations, the ozone incorporated within an alkylene carbonateliquid displays a powerful decomposition effect on dissolved organicmaterial (particularly, compounds with double bond linkages or aromaticcompounds), although the inventors of the present invention discoveredthat the alkylene carbonate itself displays only slight reactivity withozone at low temperatures, and consequently decomposition of thealkylene carbonate by the ozone is comparatively slight. Reactionbetween an alkylene carbonate and ozone generates oxidizing materials(thought to be peroxides), although ethylene carbonate liquid displaysless reactivity towards ozone than propylene carbonate, and whenethylene carbonate liquid at 40° C. was saturated with 250 mg/L of ozonegas for 5 minutes, the generation of oxidizing materials amounted to notmore than 15 mg equivalent/L.

[0040] The solvency action of alkylene carbonate liquid on an organicfilm increases with increasing temperature. Provided the temperature isbelow the flash point, the treatment operation can be performed safely,and if the treatment operation is performed in an inert gas atmosphere,then there are no problems with performing a wet treatment at atemperature of approximately 200° C. Furthermore, the vapor pressure ofalkylene carbonate at 70° C. is approximately {fraction (1/10)}th thatof other organic solvent based resist removal reagents, offering theadvantage that liquid loss through evaporation under heating is farlower. At high temperatures, this evaporation loss increases slightly,but the toxicity of the vapor is extremely low, meaning the evaporationis not a significant problem. In the present invention, because the useof ozone gas with alkylene carbonate proves very effective, wherenecessary, a draft may also be used.

[0041] The treatment liquid is easier to handle if it exists as a liquidat room temperature. If ethylene carbonate and propylene carbonate aremixed together, then increasing the amount of the latter lowers themelting point. However as described above, increasing the amount of thelatter also increases the amount of oxidizing materials generatedthrough reaction with ozone, in those cases where ozone is dissolved inthe liquid, which has an effect on the consumption of the liquid. Themixture ratio which best satisfies the requirement for a roomtemperature liquid, while suppressing the generation of oxidizingmaterials is a weight ratio of ethylene carbonate/propylene carbonatewithin a range from 4 to 2/3, and preferably from 3 to 1.

[0042] [Organic Film Removal Performance of Treatment Liquid]

[0043] A novolak type resist, which is a typically representativepositive type photoresist, comprises a cresol polymer and a polycyclicaromatic, and if such a photoresist is treated with a treatment liquidof the present invention, then the solubility increases with heating,and furthermore by dissolving ozone in the liquid a decompositionreaction can be initiated, meaning this type of film can be effectivelystripped and removed. The effective temperature range for a treatmentliquid with no dissolved ozone, using only heat, is 30 to 200° C. (40 to200° C. in the case of solely ethylene carbonate), and temperatures of60 to 150° C., which remains below the flash point, are preferred. Ifthe treatment conditions are suitable, then stripping rates of 20 μm/minor greater are easily achievable. In cases in which stripping isperformed using a treatment liquid which has been aerated with ozonegas, liquid temperatures of 20 to 60° C. are desirable. The effect ofozone is a particular feature of the present invention, and as such,treatment using ozone is described separately.

[0044] Even novolak resist film which has decomposed under ionimplantation of B⁺ at 1×10¹⁵ ions/cm², and has proved extremelydifficult to remove by conventional wet stripping methods can be removedin a reasonably short time using immersion treatment in a hightemperature alkylene carbonate liquid. For example, a film of thickness1.5 μm can be removed by a 70 second immersion treatment in alkylenecarbonate at 120° C. Resists with a decomposed layer produced by dryetching can also be removed in a similar manner. Furthermore, the higherthe treatment temperature becomes, the lower the surface tension andviscosity becomes, making high temperature treatment suitable for theresist stripping of devices with ultra fine patterns. In the case ofimmersion treatment at 120° C., the elution rate of a metal wiring filmof Al, Cu or W or the like is not more than 0.003 nm/minute.Consequently, the stripping of resists on metal films can be conductedwithout damaging the films. The reason for this characteristic is thatthe alkylene carbonate liquid is neutral. Of course, by performing thesubsequent rinse treatment with pure water, the film remains undamaged.In this manner, an alkylene carbonate liquid is chemically totally safewith respect to the substrate material, and yet also exhibits a powerfulresist stripping effect, providing a combination of characteristicswhich has been unobtainable with conventional organic solvent basedresist stripping reagents.

[0045] For a film with ion implantation of B⁺ at 1×10¹⁴ ions/cm²,stripping of a thickness of 1.5 μm is extremely fast, requiring only 5seconds (a stripping rate of 18 μm/minute) on immersion in ethylenecarbonate liquid at 120° C., and 10 seconds (a stripping rate of 9μm/minute) on immersion in ethylene carbonate liquid at 100° C. In thecase of propylene carbonate, the time taken is slightly longer. In thehigh temperature treatment of a resist that has undergone considerabledegeneration, a stripping mechanism operates wherein the components ofthe resist other than the surface layer which has undergone considerabledecomposition are dissolved readily in the treatment liquid, while thedecomposed components which are more difficult to dissolve are dispersedwithin the treatment liquid as fine particles. The fact that, asdescribed below, these dispersed fine particles can be completelydissolved by subsequent ozone gas treatment, following a reduction inthe temperature of the alkylene carbonate liquid, is a characteristic ofthe present invention.

[0046] Because the solvency action at this high temperature is extremelypowerful, just bringing a liquid film of treatment liquid of thickness10 to 100 μm in contact with an organic film on a substrate causesdissolution to begin immediately. Because the dissolution process is atype of diffusion phenomenon which accelerates with increasingconcentration difference, by forming a liquid film on the surface of theobject undergoing treatment, and then continuously or intermittentlysupplying fresh treatment liquid to the liquid film and moving theliquid, the dissolution effect can be further improved. Accordingly inthose cases in which the substrate is a wafer shape, this method caneven be applied to a single wafer spin processing in which the treatmentliquid is supplied through a nozzle, or shower treatment onto a slopedsurface.

[0047] Furthermore, oil films such as dioctyl phthalate (DOP) whichrepresents a major organic contaminant film on wafer surfaces can alsobe dissolved using high temperature treatment, and fine contaminantparticles adhered to the surface through these oil films can also beremoved at the same time. Oil films of polyethylene glycol based watersoluble processing oils left on the surface of articles followingmechanical processing can also be removed using a similar treatment.Alkylene carbonates display good solvency of a wide range of syntheticpolymers, and as described above have a large SP value, and areconsequently ideal for the removal of paint films made of epoxy resins,alkyd resins or the like with comparatively high SP values, formed onmetal surfaces. In such cases, because the treatment liquid is neutral,the surface of the mild steel, stainless steel or brass of the substrateis undamaged, even if the stripping treatment is conducted at a hightemperature.

[0048] During the removal of a film on a substrate by a liquidtreatment, by irradiating high frequency ultrasound (so-calledmegasonic) of a frequency from 0.7 to 2 MHz, and preferablyapproximately 1 MHz, through the liquid, substrate damage arising fromcavitation can be suppressed, and the chemical action of the liquid isamplified through highly accelerated molecular agitation. The vaporpressure of alkylene carbonate, even at 100° C., is not more than 10 mmHg, meaning megasonic agitation is possible at this temperature withoutthe formation of gas bubbles. By employing this treatment, the strippingperformance of the treatment liquid can be enhanced markedly. For theB⁺1×10¹⁵ ions/cm² ion implantation film described above, removal can beachieved by a 1 minute immersion treatment in ethylene carbonate at 100°C., and an acrylic resin based paint film with a slightly smaller SPvalue can be removed at 80° C. The same effects can be achieved via amethod in which the alkylene carbonate is brought in contact with thesubstrate through a liquid shower and megasonic waves are then appliedto this liquid.

[0049] [Recycling of Film Removal Treatment Reagent Liquid through OzoneAeration]

[0050] As described above, by using an alkylene carbonate liquid,organic films such as resist films can be effectively stripped andremoved, and components derived from the organic film end up dissolved(or dispersed) within the treatment liquid. If this organic materialwhich has migrated into the liquid contains double bonds or aromaticcompounds, as is the case with a novolak based resist, then by loweringthe temperature of the liquid to 50° C. or lower and aerating the liquidwith ozone gas, the organic material can be decomposed to low molecularweight material within a short time period, leaving a light colored,transparent liquid with no fine particles dispersed therein.Furthermore, it was found that the ethylene carbonate and propylenecarbonate were largely chemically unaltered by the ozone gas aeration,with the exception of the generation of a small quantity of oxidizingmaterials, and that even if the treatment liquid contained the type oflow molecular weight decomposed material described above, the resiststripping and removal performance of the liquid was not deleteriouslyaffected.

[0051] Consequently, provided the treatment liquid is aerated with ozonegas following resist film removal treatment to decompose any resistcomponents which have migrated into the liquid, the liquid can becirculated and reused, as is (if there are concerns about residualnon-decomposed resist, then microfiltration may be performed ifnecessary), as the removal treatment liquid for the resist of anothersubstrate. In other words, conducting ozone treatment offers thesignificant advantage of enabling the treatment liquid to be recycled.This ability to recycle the treatment liquid offers enormous economicbenefits when compared with conventional, expensive organic solventtreatments. In the present invention, by using a recycling techniquewherein the treatment liquid of a resist stripping treatment reagent istreated with ozone and microfiltered, the treatment liquid can be reuseddozens of times without requiring replacement with fresh treatmentliquid.

[0052] In addition, in the present invention, the step for taking thetreatment liquid following removal of an organic film and aerating withozone gas to decompose any components derived from the organic film downto low molecular weight materials may be performed using a batch method,and may also be conducted in a different area, such as a differentbuilding, from the area in which the organic film removal is performed.In such a case, where necessary a tank lorry may be used fortransporting the treatment liquid long distances to the aforementioneddifferent area.

[0053] The number of times the liquid can be circulated (in other words,the lifespan of the treatment liquid) will vary depending on thequantity of oxidizing materials generated at each ozone treatment andthe purity of the treatment liquid, which will gradually decrease. Thequantity of oxidizing materials generated by ozone treatment can bedetermined by iodometry, and the quantity will increase with increasingtemperature. The oxidizing materials are liable to be generated in amore quantity when propylene carbonate is used than when ethylenecarbonate is used, as described above. Accordingly, it is preferablethat following completion of the decomposition of a resist, nitrogen orair is immediately passed through the treatment liquid to remove theresidual ozone. This degassing process is also effective in preventingdeterioration by ozone of the liquid transport pump or the filters usedin the circulation of the liquid. Where necessary, oxidizing reactivematerials contained in the liquid following ozone removal can bedecomposed using a catalyst such as platinum or palladium.

[0054] When ozone gas is passed through and dissolved in a liquid, thedistribution coefficient D is represented by the formula D=C_(L)/C_(G),where C_(G) [mg/L] represents the ozone concentration in the gas and CL[mg/L] represents the ozone concentration in a saturated liquid.According to the literature, the solubility of ozone in a solvent isgreater for non-polar solvents such as acetic acid and di6hloromethane,for which the value of D at room temperature is approximately 1.5 to 2.In contrast, the value of D at room temperature for polar solvents isapproximately 0.4 at most, and is approximately 0.2 in the case of purewater. When ozone is dissolved in a colorless solvent, the solventbecomes a blue color, the deepness of which corresponds with the ozoneconcentration. Using this blue color of ozone water as a reference,determination of the D values at 40° C. for ethylene carbonate andpropylene carbonate through comparison with the reference yields a valueof approximately 0.25 in both cases. Furthermore, regardless of the typeof solvent, the value of D decreases as the temperature increases. Inother words, ozone becomes more difficult to dissolve. As a result ofsummarizing a large number of reports and past experiments, it becameevident that the common logarithm of the D value is represented by aninverse linear expression of the absolute temperature of the liquid, andthat the absolute temperature inverse coefficient was approximately thesame value regardless of the type of solvent. Using this finding as thebasis for an approximation, within the temperature range from roomtemperature to 100° C., every 10° C. increase in liquid temperatureresults in a decrease in the D value to approximately 8/10. Accordingly,as the D value of propylene carbonate at 20° C. is slightly less than0.4, the D value at 50° C. will fall to 0.2. Consequently, aeration withozone gas of concentration 250 mg/L will generate a dissolved ozoneconcentration in the propylene carbonate liquid of 50 mg/L. Thisconcentration is adequate for decomposing novolak resist derivedcomponents dissolved or dispersed within the treatment liquid.

[0055] [Action of Dissolved Ozone Containing Treatment Liquid]

[0056] As described above, organic film components which migrate intothe treatment liquid during the organic film removal treatment aredecomposed by ozone treatment. Consequently, if an alkylene carbonatecontaining dissolved ozone is used in the organic film removal process,then the synergistic effect of the solvency action of the treatmentliquid solvent together with the decomposition action of the ozone,results in a markedly improved stripping and removal performance evenfor treatment temperatures of 60° C. or lower.

[0057] In the immersion treatment of a novolak based resist which hasnot undergone ion implantation (and has therefore not degenerated), if aozone saturated propylene carbonate is used, then in comparison withpropylene carbonate containing no dissolved ozone, a 5 fold increase instripping rate can be achieved at 20° C., and a greater than 2 foldincrease can be achieved at 30 to 40° C.

[0058] For a film of thickness 1.5 μm with ion implantation of B⁺ at1×10¹⁴ ions/cm², immersion in ozone saturated ethylene carbonate at 50°C. leads to complete decomposition in several minutes, and the resultingliquid is transparent, with no dispersed fine particles of removedresist. In a case in which a high concentration ion implanted resistfilm is stripped using only a high temperature alkylene carbonateliquid, the small quantity of fine particles of degenerated resist whichremain adhered to the surface can be completely removed by subsequentrinsing with an ozone saturated alkylene carbonate liquid.

[0059] In the case of a cyclized isoprene-based resist, which is atypically representative negative type resist, the decomposition byozone of polyisoprene, which represents a major component of the resist,is extremely fast, and because the photo-crosslinked azide compoundtypically employs an aromatic compound, this type of resist film can bestripped with an ozone saturated treatment liquid at an even faster ratethan a novolak based resist.

[0060] In the case of an organic film removal in which the treatmentliquid contacts the substrate surface in the form of a moving liquidfilm, if the treatment liquid is saturated with ozone in an ozonesaturation vessel and then supplied to the substrate surface through anozzle, then similar excellent removal effects to those described abovecan be achieved. In order to achieve the required ozone concentration,the temperature of the liquid should preferably be not more than 50° C.At high temperatures the ozone concentration decreases, and consequentlythe piping linking the ozone saturation vessel and the nozzle within theorganic film removal apparatus should be kept as short as possible. If amegasonic spot shower is used as the nozzle, then the stripping rate canbe improved even further. This method is particularly useful if aprocess requires a powerful stripping treatment at a temperature of 50°C. or lower, such as in the case of a dry etched resist.

[0061] A simple method which employs the action of ozone in a singlewafer processor for removing an organic film from a substrate can beprovided by a liquid film formation treatment in which a treatmentliquid and ozone gas are projected simultaneously onto the substratesurface. In such a case, very little ozone dissolves in the treatmentliquid, although projection of room temperature propylene carbonateenables the stripping of a cyclized isoprene based resist, and thestripping rate falls very little from immersion treatment with ozoneaeration. Furthermore, this simple method also offers satisfactorystripping of novolak based resist films which have not undergonedegeneration. For example, in a continuous treatment process for a largeglass substrate for use in a liquid crystal application, wherein theglass substrate is moved within the plane of the substrate surface, inthose cases in which resist stripping is performed by spraying on atreatment liquid, then by providing a slope for a liquid film to moveacross the substrate surface, a simple method in which the treatmentliquid and ozone gas are projected simultaneously onto the substratesurface can be utilized.

[0062] As alkylene carbonate exhibits the D value temperature dependencydescribed above, ozone dissolution at 80° C. is D=0.05. At thistemperature, the ozone dissolved in the liquid decays very rapidly,although it provides an extremely powerful decomposition action.Accordingly, in order to effectively increase the stripping performancein a high temperature liquid film treatment, the concentration of theozone gas contacting the liquid film surface should be maintained at amaximum. In the liquid film, the ozone concentration of the liquid willmomentarily reach a balance with the ozone concentration of the gas,providing the liquid film with an ozone concentration sufficient toachieve the desired effect. In order to achieve this effect, anapparatus is required in which the thickness of the ozone gas spaceabove the treatment surface is kept very thin so that the air initiallycontacting the liquid film can be substituted with ozone gas in as shorta time as possible. According to such a technique, even a resist film ofthickness 1.5 μm which has undergone ion implantation of B⁺ at 1×10¹⁴ions/cm² can be removed within 30 seconds, including the subsequentrinse, by treatment at 80° C., enabling a single wafer spin processingto be effectively utilized with a good level of productivity.

[0063] Because both ethylene carbonate and propylene carbonate have ahigh boiling point, if they are used for rinsing, and a subsequent spindrying process is then performed, then a film of molecules of thesecompounds will remain adhered to the wafer surface. Consequently, asubsequent rinse with ultra pure water should preferably be performed.In the case of rinsing with pure water, once a wafer surface dries, ifthe surface is silicon then the air causes a natural oxide film to formimmediately, and any residual fine particles are trapped by this filmmaking removal by pure water rinsing difficult. In contrast in the caseof an ethylene carbonate liquid rinse, if the substrate is cooled toroom temperature with an ultra thin liquid film still on the surface,then the ethylene carbonate liquid film solidifies. This offers anadvantage in that the substrate surface is separated and protected fromthe surrounding atmosphere by this solidified film. The substrate canthen be transported to a separate pure water rinse system and rinsedwith water.

[0064] [Use of Complexing Agents (Chelating Agents)]

[0065] As described above, an alkylene carbonate liquid is useful as atreatment liquid which can be circulated and reused for the strippingand removal of organic films from substrates, although metal impuritiesin the resist accumulate within the liquid as the number of repeateduses of the liquid increases. Because the liquid is neutral, there is adanger of these metal impurities adhering to, and contaminating thestripped substrate surface. However, if an aliphatic carboxylic acidbased complexing agent (chelating agent) is added to the treatmentliquid, then not only is there a decrease in the likelihood of metalimpurities of Fe, Ni, Cr, Cu, Zn and Al adsorbing to a silicon surfaceor an oxidized surface or the like, but even contamination by Na and Kcan be reduced.

[0066] In those cases where, as described above, an aliphatic carboxylicacid based complexing agent (chelating agent) is added to the treatmentliquid, typically between 0.01 and 2% by weight of the aliphaticcarboxylic acid based complexing agent is incorporated relative to theamount of ethylene carbonate, propylene carbonate, or a mixture ofethylene carbonate and propylene carbonate. Examples of the aliphaticcarboxylic acid based complexing agent include tartaric acid, citricacid and oxalic acid, although of these, tartaric acid and citric acidare preferred as they offer low toxicity and are capable of complexing alarge variety of metals. The amount of these acids added is as describedabove, although quantities from 0.03 to 1.5% by weight are preferred. Ifthe quantity of added acid is too large, then the ethylene carbonateand/or the propylene carbonate itself is more likely to undergodecomposition, whereas if the quantity is too small, the metal capturingperformance is limited.

EXAMPLES

[0067] As follows, an organic film removal method and apparatusaccording to the present invention are described in detail using aseries of examples. However, the present invention is in no wayrestricted to the examples presented below.

[0068] The ozone gas used in the following examples was produced bypassing oxygen containing 0.4% of nitrogen through a discharge typeozone generation device at a rate of 2 to 10 L/minute, and what isdescribed below as high concentration ozone gas refers to a gas with anozone concentration of approximately 250 mg/L. The ethylene carbonateand propylene carbonate used was of guaranteed reagent grade purity.

[0069] Furthermore, in a production process for an advanced ultra LSI,minimal quantities of organic matter (an organic carbon concentration ofnot more than 2×10¹³ atoms/cm²) on the wafer surface are required, andin the following examples, the absolute quantity of residual organiccarbon on top of a silicon oxide film following resist stripping wasdetermined in accordance with the sample preparation method disclosed inJapanese Laid-open publication (kokai) No. 2000-39410 (JP2000-39410A),which is a highly sensitive charged particle radioactivation analysismethod in which ¹³N generated by nuclear reaction of ¹²C(d,n)¹³N ischemically separated, and the β⁺ annihilation radiation emitted by this¹³N is then measured by a pair of detectors operated in coincidence.

[0070] [Example 1]

[0071]FIG. 1 shows a schematic illustration of an apparatus in which acassette containing a plurality of wafers with resist films is immersedin an ozone gas aerated ethylene carbonate molten liquid to remove theresist films.

[0072] A draft built for the experiments is divided into a front chamber1, a treatment chamber 2 into which cleaned air is introduced, and arear chamber 3. Opening glass doors are provided on all surfaces,although during operation the inside of the draft is isolated from theexternal atmosphere. The valves described below are all electromagneticvalves, and operation of these valves, a liquid transport pump, and arobot (for transporting the cassette) are all performed from outside thedraft.

[0073] In order to enable a quartz glass cassette 5 capable of holding 7six inch wafers 4 to be moved from the front chamber 1 into thetreatment chamber 2, which has an exhaust outlet in the rear (not shownin the diagram), and then pass through the rear chamber and be removedfrom the draft following treatment, the front chamber 1 and the rearchamber 3 are provided with an air exchange mechanism (not shown in thediagram) and opening doors 6 which prevent the ozone gas containingatmosphere inside the treatment chamber from leaking outside the draft.

[0074] Quartz glass vessels 7, 8 and 9 are positioned inside thetreatment chamber 2. The vessel 7 is a vessel containing approximately 3L of ethylene carbonate for treating the cassette, the vessel 8 is avessel for performing a spray rinse with unused ethylene carbonate, andthe vessel 9 is an overflow rinse vessel using ultra pure water.

[0075] Ethylene carbonate liquid is supplied to the vessel 7 via asupply pipe 10. An ozone gas diffuser 11 and a heater 12 for maintainingthe immersion treatment liquid at a predetermined temperature areprovided in the bottom portion of the vessel, and the former isconnected to a gas inlet pipe 14 which supplies gas from an ozone gasgeneration device (not shown in the diagram) via a valve 13. The wafercontaining cassette 5 is moved into the treatment chamber using a robotarm 15 (the robot itself is not shown in the diagram), and then loweredinto the treatment liquid of the vessel 7 and immersed for apredetermined period of time. The cassette 5 is then transported to thevessel 8. An ethylene carbonate liquid spray nozzle 16 is attached tothe tip of a horizontally rotating arm 17, and this spray nozzle ispositioned over the vessel 8 only when the cassette has been set insidethe vessel. The rotational axis 18 of this arm is operated by a rotationmechanism 19. The arm and the rotational axis also perform the functionof a rinse liquid transport pipe, and are connected, inside the rotationmechanism 19, to a rinse liquid supply pipe 21, which is linked to aliquid storage tank with a pressurized supply function (not shown in thediagram) via a valve 20.

[0076] Following completion of the spray rinse using ethylene carbonateliquid, the cassette is transported by the robot to the vessel 9, andsubjected to an overflow rinse in ultra pure water supplied through asupply pipe 23 via a valve 22. Numeral 24 represents a stainless steelouter vessel, and numeral 25 represents a waste water pipe.

[0077] The vessel 7 and the vessel 8 are each attached to a chemicalsupply vessel, 26 and 27 respectively, constructed of a fluororesin,which are provided in a liquid supply systems chamber 28 positionedunderneath the treatment chamber. At the top of the vessel 27, a rinsewaste liquid collection pipe 29 is connected to the narrowed bottom edgeof the rinse vessel 8 via a valve 30. Furthermore, a treatment liquidsupply pipe 31 for introducing ethylene carbonate liquid is provided atthe base of the vessel 27, and this treatment liquid supply pipe 31 isconnected to a liquid storage tank with a pressurized supply mechanism(not shown in the diagram) via a valve 32. The liquid in the vessel 27is first transported to the vessel 26, and this transfer is achievedthrough a connection pipe 34 provided with a liquid transport pump P anda three way valve 33. The numerals 35 represent gas exhaust pipes.

[0078] A liquid waste pipe 36 provided at the base of the vessel 7 isconnected to the roof section of the vessel 26 via a valve 37.Furthermore, a gas diffuser 38, which is connected to an inert gassupply pipe 40 via a valve 39 and enables aeration with an inert gas(nitrogen or ultra pure air), is provided inside the vessel 26, towardsthe bottom of the vessel. A discharge pipe 42 enabling discharge ofliquid via a valve 41 is provided in the base of the vessel 26. Liquidinside the vessel 26, from which ozone has been removed through thedegassing process with inert gas, is passed through a fine particleremoval precision filter F (constructed of a fluororesin) using theaction of a liquid transport pump P, and is then pumped through thesupply pipe 10 to the vessel 7.

[0079] Because the melting point of ethylene carbonate is 36° C., thevessels 26 and 27 are provided with internal heaters 12 near the bottomof each vessel for maintaining the temperature of the treatment liquidat 40° C. or greater. Furthermore, the ethylene carbonate liquid storagetank is also provided with a heater, and solidification of ethylenecarbonate within the treatment system is prevented by using afluororesin or the like for most of the piping for the liquid, and alsowrapping the piping in an insulating material. In other words, thesections drawn in solid bold lines in the diagram are equipped withinsulation measures for maintaining the internal temperature at 40° C.or greater.

[0080] The apparatus described above was used to investigate the resiststripping action of ethylene carbonate liquid at a liquid temperature of40° C. The samples used were oxidized six inch silicon wafers, which hadbeen surface treated with HMDS, and a 1.5 μm novolak resin based i-lineradiation positive resist (product name: IX555, manufactured by JSRCorporation) then applied and baked at 140° C. for 60 seconds. First,one of these wafers was set in the cassette, while a high concentrationozone gas was bubbled through the ethylene carbonate molten liquid inthe vessel 7 for 5 minutes at a rate of 2 L/minute. Once it had beenconfirmed that the 42° C. liquid had turned a slight blue color as aresult of the dissolved ozone, the cassette was immersed in the liquid,and by observing the progress of the stripping of the resist with thenaked eye, it was confirmed that the resist had been entirely strippedaway after 4 seconds (a stripping rate of 22.5 μm/minute). Subsequently,the cassette was immediately raised out of the liquid, subjected to atwo second spray rinse with ethylene carbonate in the vessel 8, and thensubjected to overflow rinsing with ultra pure water for 3 minutes in thevessel 9. After subsequent spin drying, the surface of the wafer wasinspected with a microscope, and no non-stripped sections were visible.The liquid temperature in the vessel 7 immediately following the raisingof the cassette was 40° C.

[0081] In contrast, when a cassette with a single sample was immersed inthe vessel 7 in a similar manner but without the bubbling of ozone,observation with the naked eye suggested the stripping was completed in5 seconds (a stripping rate of 18 μm/minute). At 40° C. the solvencyaction of the ethylene carbonate itself, is high, and even withoutpassing ozone gas through the liquid, the resist can still be removed ina short period of time. Following stripping of the resist, the liquidwas a pale yellow color.

[0082] Next, seven wafers were inserted into a cassette, filling all theavailable slots, and in a similar manner to that described above, ozonewas bubbled through the liquid in the vessel 7, and the cassette wasthen immersed for 6 seconds, before being spray rinsed with ethylenecarbonate for 4 seconds in the vessel 8. The spray nozzle 16 utilized afull cone ceramic spray nozzle, with a spray rate of approximately 500mL/minute. Following a 5 minute ultra pure water rinse in the vessel 9and subsequent spin drying, the resists from each of the wafers wereconfirmed by naked eye inspection as being totally removed. A 2 cm×2 cmchip was then cut out of each wafer, and the quantity of residualorganic carbon (atoms/cm²) was determined by charged particleradioactivation analysis. The average result was 1.8×10¹³, with amaximum value of 2.1×10¹³, indicating that the resist, including theHMDS layer, had been satisfactorily removed. Following removal of thecassette, the ethylene carbonate liquid was not a pale yellow color, butrather a pale blue color, indicating quite clearly that decomposition byozone of components of the stripped resist is occurring within theliquid.

[0083] [Example 2]

[0084] As confirmed by the results of the example 1 above, the strippedresist components are decomposed by the ozone, and consequently thetreatment liquid used in the resist stripping process should be able tobe reused several times. Using the same apparatus described in FIG. 1,the action of the recycling mechanism for the treatment liquid isdescribed below.

[0085] Using a cassette capable of holding 7 samples of identicalspecification to those described in the example 1, the stripping,rinsing and drying processes were performed in the same manner as theexample 1.

[0086] In the vessel 7, following the raising of the cassette, ozone gaswas bubbled through the liquid for a further one minute to decompose thedissolved resist, and the valve 37 was then opened, and all of theliquid in the vessel 7 was transferred to the vessel 26. Subsequently,the valve 39 was opened, and nitrogen gas was bubbled through theliquid. Within one minute, the ozone dissolved in the liquid had beenremoved, and the liquid was then pumped out of the vessel 26 by theliquid transport pump P, passed through the precision filter F, and thefiltered ethylene carbonate liquid was then returned to the vessel 7.The valve 11 was then opened and ozone gas was bubbled through theliquid for 5 minutes, in the same manner as the example 1, and the nextcassette treatment was then performed.

[0087] This resist stripping and decomposition / ozone degassing ofliquid / filtering cycle was repeated 30 times. In other words, usingozone aerated ethylene carbonate liquid at 40° C., 210 wafers withresist films of identical specification were subjected to resiststripping, and the resist stripping action for the samples of the finalcassette was still quite satisfactory. Accordingly, even after 30repeated cycles of the stripping process, or in other words 5 hours ofcontinuous apparatus operation with the same liquid, there was nodeterioration in the resist stripping action of the ozone containingethylene carbonate liquid, indicating that there was effectively nodecomposition or deterioration of the ethylene carbonate itself. Thisfinding suggests that in comparison with typical solvent treatments inwhich the stripping action of the solvent deteriorates as the quantityof dissolved resist increases, the present invention offersextraordinary advantages. In the type of continuous operation mentionedabove, even if the time required for resist stripping is 3 minutes,repeated stripping treatment can still be performed with a similar tacttime to conventional multiple tank immersion cleaning apparatus ofapproximately 10 to 15 minutes.

[0088] In these repeated operations, the rinse liquid in the vessel 8passes through the open valve 30 and collects in the vessel 27.Following the completion of a predetermined number of treatments, theliquid in the vessel 7 is transferred to the vessel 26 and is thendischarged into a waste liquid vessel (not shown in the diagram) via thevalve 41. Subsequently, the valve 33 is opened, and the ethylenecarbonate liquid in the vessel 27 is replenished, and this liquid isthen passed through the vessel 26 and transferred to the vessel 7. Fromthis point, the operation described above can be repeated.

[0089] [Example 3]

[0090] Propylene carbonate is a liquid at room temperature, withchemical properties similar to those of ethylene carbonate liquid, andconsequently the same apparatus as that described in FIG. 1 was used toinvestigate the resist stripping and removal action of propylenecarbonate.

[0091] A single wafer sample of the same specifications as that used inthe example 1 was placed in a cassette, and using the same treatmentconditions as those described for the single wafer treatment in theexample 1, with the exception of replacing the ethylene carbonate withpropylene carbonate, and following the same process as the ozone gasaerated sample described in the example 1, the temperature dependency ofthe stripping performance was investigated. The results are shown inTable 1. In Table 1, the determination of the stripping time requiredwas judged by naked eye observation, and the figures for stripping ratewere then calculated from these times.

[0092] The ozone concentration of a liquid is typically determined byiodometry, that is, by the amount of oxidation of potassium iodide(equivalent to the quantity of generated iodine). It is already knownthat the solubility of ozone in a liquid decreases as the temperature ofthe liquid increases, and consequently, as the temperature of an ozonecontaining liquid is increased, typically the quantity of iodinegenerated by iodometry should decrease. However, in the case ofpropylene carbonate, the propylene carbonate molecule itself reacts withthe ozone, forming a separate oxidizing material, and it is thought thatthe quantity of this material increases with increasing temperature ofthe liquid. In other words, as a result, the quantity of iodinegenerated through iodometry actually increases with increasingtemperature. Taking the quantity of iodine generated at 20° C. to be 1,the proportional quantities of iodine generated at each temperature areshown in the table. TABLE 1 Stripping Quantity of Immersion timerequired Stripping rate Iodine generated temperature (° C.) (seconds)(μm/minute) by iodometry 20 12   7.5 1   30 7 12.8 1.38 40 4 22.5 1.75

[0093] The stripping test results on wafers of the same specifications,but for the case in which ozone gas was not bubbled through thepropylene carbonate vessel, are shown in Table 2. TABLE 2 ImmersionStripping time Stripping rate temperature (° C.) required (seconds)(μm/minute) 20 55 1.6 30 15 6.0 40  8 11.3 

[0094] As is shown in Table 2, even if ozone gas is not bubbled throughthe liquid, the stripping rate still increases markedly as the immersiontemperature is raised. The reason for this observation is that as thetemperature of the liquid is increased, the solvency action on theresist improves. If ozone gas is passed through propylene carbonate, thecolor of the liquid changes to a pale blue, and as the temperature ofthe liquid is raised the strength of this blue color diminishes,although even at 40° C. a very pale blue color is still visible. Incomparing the results in Table 1 and Table 2 it is evident that at aliquid temperature of 20° C. where the ozone concentration iscomparatively high, ozone aeration of the liquid produces anapproximately 5 fold increase in the stripping rate over the case of noozone aeration. In contrast, at 30° C. and at 40° C., the increase instripping rate is only approximately two fold. However, even the liquidfollowing the stripping treatment displays a very pale blue color withozone aeration, indicating that even though the concentration of solubleozone decreases with increasing liquid temperature, the dissolved ozonestill displays an organic material decomposition effect. Moreover, thereis a possibility that the oxidizing materials generated from thepropylene carbonate are contributing to the observed increase instripping rate, although this effect is unlikely to be highlysignificant.

[0095] Two wafers of the same specification were treated using animmersion temperature of 40° C., with an immersion time of 6 seconds inthe case of ozone aeration and an immersion time of 10 seconds in thecase of no ozone gas aeration, and were both then subjected to a 4second spray rinse with propylene carbonate and a 5 minute rinse withpure water. A 2 cm×2 cm chip was then cut out of each wafer, and thequantity of residual organic carbon was determined by charged particleradioactivation analysis. The result was 1.7×10¹³ atoms/cm² for theozone aerated sample and 2.0×10¹⁴ atoms/cm² for the non-aerated sample,indicating that provided ozone is added, propylene carbonate produces asatisfactory resist stripping action with a similar fast stripping rateto that of ethylene carbonate liquid.

[0096] [Example 4]

[0097] From the results of the examples 1 through 3 described above, itis apparent that a marked improvement in stripping rate can be expectedon heating, for both ethylene carbonate liquid and propylene carbonate.Furthermore, both compounds have a high boiling point and a high flashpoint, and treatment at temperatures of up to 150° C. pose no danger.Consequently, using the apparatus of FIG. 1, the stripping action at notless than 40° C. was investigated for a resist film which had beensubjected to high concentration ion implantation, which represents aresist film which conventionally cannot be satisfactorily removed unlessashing is used.

[0098] The samples used were oxidized six inch silicon wafers to which a1.5 μm novolak resin based positive resist (product name: IX500,manufactured by JSR Corporation) had been applied (without preliminarytreatment with HDMS) before baking at 130° C. for 4 minutes, and whichhad then been subjected to 30 keV ion implantation of ¹¹B⁺ across theentire wafer surface at either 1×10¹⁴ ions/cm² or 1×10¹⁵ ions/cm².

[0099] Without performing ozone aeration of the vessel 7 of FIG. 1, theliquid temperature inside the vessel 7 was raised to 40° C., and asingle 1×10¹⁴ ions/cm² implantation sample was placed in a cassette andimmersed, and the resist stripping performance was observed with thenaked eye. With either ethylene carbonate or propylene carbonate, after5 minutes immersion the resist surface had become jagged and a portionof the resist had been dissolved, but when separate 1×10¹⁴ ions/cm²implantation samples were treated with the immersion temperature raisedto 60° C., the resist film was able to be completely stripped, in 1minute and 40 seconds in the case of ethylene carbonate liquid, and in 2minutes 20 seconds in the case of propylene carbonate. The strippingrates were 0.9 μm/minute and 0.6 μm/minute respectively, which ifapplied to a batch immersion treatment process, represent sufficientlyfast stripping rates as to be viable. When the samples were rinsed anddried in the same manner as the examples described above, and thequantity of surface residual organic carbon was determined by chargedparticle radioactivation analysis, the results were 3.1×10¹³ atoms/cm²and 3.4×10¹³ atoms/cm² respectively, representing a level of resiststripping which is almost satisfactory.

[0100] Using these B⁺1×10¹⁴ ions/cm² implantation samples, thetemperature dependency of the stripping rate for samples immersed inheated ethylene carbonate liquid or propylene carbonate wasinvestigated. The results are shown in Table 3. TABLE 3 Ethylenecarbonate liquid Propylene carbonate Stripping Stripping Liquid timeStripping time Stripping temperature required rate required rate (° C.)(seconds) (μm/minute) (seconds) (μm/minute) 60 100 0.9 140 0.6 80 40 2.360 1.5 100 10 9 14 6.4 120 5 18 6 15

[0101] For both compounds, the stripping rate increases markedly withincreasing immersion temperature. Even at 120° C., the vapor pressure isnot particularly high, and any vapor can be exhausted with ease.Furthermore, because the toxicity of the vapor is low, even this type ofhigh temperature treatment has little effect on people.

[0102] Ethylene carbonate displays a slightly superior strippingperformance to propylene carbonate. Considering the strippingperformance at temperatures of 100° C. or greater, single substratetreatment is possible simply by heating the treatment liquid.

[0103] If the amount of ion implantation is 1×10¹⁵ ions/cm² or greater,then the degenerated sections of the resist undergo considerablehardening, and as a result, complete dissolution is difficult even withethylene carbonate liquid, and for samples in which the entire resistfilm on a wafer surface has been subjected to ion implantation,stripping of the resist leads to fine particles of undissolved resistbecoming dispersed within the liquid. Actual resists subject to resiststripping treatment typically comprise a fine pattern, and consequentlyusing the ion implantation wafers prepared in the manner described aboveas samples for a stripping test would represent a test which is overlydifferent from actual treatment conditions. Consequently, a 1 mm squaregrid pattern of light scratches was formed in the surface of the aboveion implantation resist films using a diamond dicer, and these scratchedresist films were then subjected to stripping treatment. The results areshown in Table 4. TABLE 4 Liquid temperature Stripping time required(seconds) (° C.) Ethylene carbonate Propylene carbonate  80 210 200 100100 110 120  70  70

[0104] High concentration ion implantation is typically performed onresists formed on an oxide film or a nitride film, and because thesetreatment liquids are neutral organic compounds, it is though thatdeleterious effects on such oxide films or the like are extremelyunlikely, even for immersion for approximately 3 minutes at atemperature of 100° C. or greater. Accordingly, even high concentrationion implantation samples of 1×10¹⁵ ions/cm² or greater should be able tobe satisfactorily removed by immersion treatment at temperaturesexceeding 100° C. by as much as is practical (for example, 200° C.).

[0105] [Example 5]

[0106]FIG. 2 shows an apparatus for performing stripping via singlewafer spin processing using ethylene carbonate liquid. The mechanism forperforming the single substrate spin treatment comprises a support 43for supporting a six inch wafer 4′, a rotational axis 44, and a drivesection 45, enabling the wafer 4′ on top of the support 43 to be spunaround at a variable speed from a slow speed to a high speed, and thismechanism is housed inside a chamber 47 with a bottom 46. Ethylenecarbonate liquid is heated inside a vessel 49 equipped with a heater 48capable of heating the liquid to a predetermined temperature such as100° C., and is stored in a liquid state. By operating a three way valve50, a liquid transport pump P pumps the liquid through a fine particleremoval filter F and a pipe 51, and the liquid is then supplied onto thesurface of the wafer 4′ through a nozzle 52 provided at the tip of thepipe 52, at a flow rate of 1 to 2 mL/minute.

[0107] The ethylene carbonate liquid, which has been heated to a hightemperature, dissolves the resist in an extremely short period of time,and the centrifugal movement of the liquid film effectively removes thedissolved material. Depending on the difficulty of the actual strippingand the temperature at which the treatment is performed, the strippingtreatment time may vary from several dozen seconds down to severalseconds. The rotational speed should preferably be from 100 to 200 rpm.In those cases in which a rinse is then performed, the rinse may beperformed in several seconds at a rotational speed of approximately 1000rpm. The treatment liquid which has dissolved the resist and then falleninto the bottom of the chamber is first transferred to a waste liquidcooler 54 via a pipe 53. Following cooling to approximately 40° C., theliquid passes through a valve 57 and drops down a pipe 58 into a vessel56 provided with a heater 55 for maintaining the temperature at 40° C.Once the liquid inside the vessel 56 has reached a predeterminedquantity, ozone gas supplied from an ozone gas generation device (notshown in the diagram) is passed through valves 61, 60 and a diffuserpipe 59, and is bubbled through the liquid using a diffuser 62. Thisozone gas aeration causes the resist components either dissolved ordispersed within the ethylene carbonate liquid to rapidly decompose viathe generation of ozonides, and the liquid in the vessel, which was ayellow color following resist stripping, rapidly changes to a colorlessor pale blue transparent liquid.

[0108] During this process, the ethylene carbonate liquid is chemicallyquite stable with respect to the ozone, although small quantities ofoxidizing reaction products (thought to be peroxides) are generated.These products have almost no effect on the resist strippingperformance, although the quantity of these materials graduallyincreases with increasing ozone treatment time, and because thegeneration of these oxidizing materials results in a gradualdegeneration of the liquid, such reactions must be suppressed as far aspossible. Accordingly, once ozone aeration has dissolved the resist andthe liquid has become either colorless or a pale blue color, the valve61 is closed and the ozone gas aeration is halted. Next, using a valve63 connected to a nitrogen gas supply line, nitrogen gas is bubbledthrough the liquid in the vessel 56, and any dissolved ozone is removed.This completes the recycling of the ethylene carbonate liquid. Therecycled liquid is then transferred through a connecting pipe 65 to avessel 67 equipped with a heater 66, using the action of a valve 64 anda liquid transport pump P. Once the liquid inside the vessel 67 hasreached a predetermined quantity, the liquid is heated to apredetermined temperature, and is then supplied to the spray nozzle 52through a recycled liquid supply pipe 68, using the three way valve 50and the liquid transport pump P. The recycled liquid replaces the supplyof new liquid from the vessel 49, and from this point, the liquid inthis vessel 49 is used only for spray rinsing. A valve 69 is connectedto a pipe 70 leading to a liquid storage tank (not shown in thedrawing), and is used for supplying new liquid when required. Numeral 71is a waste liquid valve, and numeral 72 represents an exhaust gasoutlet.

[0109] A second nozzle 73 inside the chamber is connected to a cold airsupply pipe 74 for supplying cooled air from a cooler (not shown in thediagram) via a valve 75. Following completion of a high temperatureethylene carbonate liquid rinse, the wafer is rotated at 2000 to 3000rpm for approximately 5 seconds to remove any liquid from the wafersurface, and cold air is then blown onto the wafer from the nozzle 73,solidifying the thin film of residual ethylene carbonate on the wafersurface.

[0110] Transfer of a wafer to, and subsequent removal from the apparatusis performed by a robot (not shown in the diagram), which removes awafer from the cassette, opens the lid 76 of the chamber 47, and thensets the wafer on the support 43. The lid 76 is then closed and thestripping treatment described above is carried out, and on completion ofthe treatment, the robot sets the wafer, with a solid ethylene carbonatefilm formed on the wafer surface, into a water rinsing cassette. Whenthe water rinsing cassette has been filled, the wafers are rinsed withultra pure water and then dried in a typical rinsing and dryingapparatus, thereby completing the stripping process.

[0111] Regardless of whether the sample is a novolak resin basedpositive resist, a chemically amplified polyvinylphenol derivative basedpositive resist, or a cyclized polyisoprene based negative resist, byperforming treatment at a liquid temperature of 80° C. or greater, evensamples that have been subjected to considerably intense post baking,such as those treated at 140° C. for approximately 3 minutes, can bestripped within 10 seconds for a resist film of thickness 1 μm. Thestripping rate is at least 6 μm/minute. In this type of strippingprocess, the treatment time including the rinse time is extremely short,and moreover because the ethylene carbonate liquid itself is neutral,metal films of Al, Mo, W, Ti or ITO and the like used for wiring areleft effectively undamaged.

[0112] An oxide film which had been subjected to dry etching with a CFbased reactive gas and consequently comprised a degenerated resist onthe surface, which represents a resist which is typically removed byashing with an oxygen plasma, was used as a treatment sample. The sampleemployed a TEG wafer with a pattern similar to an actual device patternformed thereon, and the resist was a novolak resin system TFR-910PM(product name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) with a filmthickness of 1.2 μm. Treatment was performed for 15 seconds usingethylene carbonate liquid at 100° C. and a rotational speed of 200 rpm,rinsing was then performed for 5 seconds using the same treatment liquidat 1000 rpm, and then the liquid was removed through centrifugal actionby spinning at 2500 rpm for 5 seconds. Following solidification of theresidual ethylene carbonate on the wafer surface by cold air, the samplewas subjected to an ultra pure water rinse and then drying in anotherwafer rinser/drier for a single substrate. Observation of the samplesurface using an electron microscope reveled that the resist had beencompletely removed. In addition, the resist stripping rate was 5μm/minute.

[0113] [Example 6]

[0114] Using single wafer spin stripping, an example is presented inwhich an effective treatment is achieved by spraying room temperaturepropylene carbonate liquid and ozone gas simultaneously onto a resistsurface.

[0115] The apparatus shown in FIG. 2 was used, although modificationswere made so that propylene carbonate was initially supplied to thevessel 49, the heaters provided in each of the vessels were not used,and the cold air supply pipe 74 was converted to an ozone gas supplypipe, enabling high concentration ozone gas to be supplied at a flowrate of 5 to 10 L/minute simultaneously with the propylene carbonateliquid supply. In addition, a separate nozzle and piping system wereprovided to enable a stream of high pressure nitrogen gas to be directedat the center of the wafer during the drying stage. With the exceptionof these modifications, treatment was performed in the same manner asthe example 5.

[0116] The wafer used for the stripping test was of the samespecifications as that used in the example 1. Under conditions includinga temperature of 25° C. and 200 rpm, observation with the naked eyerevealed that stripping required 10 seconds. The stripping rate was 9μm/minute. Treatment was continued for a further 5 seconds, a rinsetreatment was then performed at 1000 rpm for 5 seconds, and then highpressure nitrogen gas was blown onto the center of the wafer and spindrying was performed at 2500 rpm. Following this drying treatment, thewafer was then subjected to a further rinse in ultra pure water and spindrying using a separate rinser/drier, in a similar manner to theprevious example. Charged particle radioactivation analysis of theresidual carbon on the wafer surface revealed a result of 1.9×10¹³atoms/cm², indicating satisfactory stripping of the resist.

[0117] [Example 7]

[0118] As described above, increasing the treatment liquid temperaturecauses a decrease in ozone solubility, and so in the system described inthe example 6 above, the ozone concentration in the propylene carbonateliquid film on the wafer surface will not reach a satisfactory value,and so no large improvement in stripping performance can be expectedwith increased temperature.

[0119] Consequently, the apparatus was modified as shown in FIG. 3,which represents an example in which ozone gas is supplied onto a wafersurface within a restricted, comparatively thin, layer-like space. Thosesections not shown in FIG. 3 are identical with those of FIG. 2. Theoperation of those sections is as described in the example 5.

[0120] In FIG. 3, the chamber 47 is provided with a bearing 79 for arotatable propylene carbonate liquid supply pipe 78 capable ofdischarging a liquid from a propylene carbonate discharge outlet 77 atthe tip of the supply pipe 78 onto the center of the wafer 4′, at thesame flow rate described in the example 5, as well as a bearing 82 for arotatable gas supply pipe 81 for emitting a stream of high concentrationozone gas from an emission outlet 80 at the tip of the gas supply pipe81 onto the center of the wafer 4′, wherein both the propylene carbonateliquid supply pipe 78 and the gas supply pipe 81 are positioned over thewafer 4′ only during the period the wafer 4′ is mounted on the support43.

[0121] In addition, a roof-like quartz glass hood 83 is also providedwhich covers the entire wafer surface during the period in which ozonegas is projected onto the wafer surface, so that with the exception ofthe sections occupied by the liquid supply pipe and the ozone gas supplypipe, the layer above the wafer surface is approximately 5 mm. Duringinsertion and removal of wafers, the hood is raised upwards togetherwith the lid section, and set aside until needed. The propylenecarbonate supply pipe 78 is connected to the fine particle removalfilter F shown in FIG. 2, whereas the gas supply pipe 81 is connected toa high concentration ozone gas generation device (not shown in thediagram) capable of a gas flow rate of 4 L/minute. In a location closeto a valve 84, the pipe from the ozone gas generation device isconnected, via a three way valve 85, to a cylinder 87 which stores theozone gas from the generation device temporarily and can dischargeapproximately 2 L of ozone gas from the emission outlet 80 within anapproximately 10 second period, using the action of an automatic piston86. This cylinder is surrounded with a heater 88 to enable the ozone gasinside the cylinder to be heated. In addition, the nozzle and pipingsystem provided in the chamber 47 of the example 6 to enable a stream ofhigh pressure nitrogen gas to be directed at the center of the waferduring the drying stage were also provided in this modified example.

[0122] Stripping and removal of a resist is conducted in the mannerdescribed below. A 1×10¹⁴ ions/cm²B⁺ ion implantation wafer from theexample 4 was used as a test sample. First, high concentration ozone gaswhich has been heated to approximately 80° C. (the heater is not shownin the diagram) is fed through the fluororesin three way valve 85 andinto the cylinder 87 with the piston 86, for a period of approximately30 seconds, filling the approximately 2 L storage capacity of thecylinder 87. Numeral 88 represents the heater for maintaining thetemperature of the gas. The lid 76 and the attached hood 83 are thenraised, and a wafer 4′ is mounted on the support 43. The liquiddischarge outlet 77 and the gas emission outlet 80 are then rotated intoposition over the center of the wafer, and the lid is closed, loweringthe hood 83 and covering the entire surface of the wafer. The wafer isthen slowly rotated at approximately 60 rpm, and propylene carbonateliquid which has been heated to 80° C. in the liquid vessel 49 isdischarged onto the wafer for approximately 5 seconds using the liquidtransport pump P, immediately forming a heated propylene carbonateliquid film across the entire wafer surface. If the rotation is brieflyhalted at this point, the three way valve 85 and the valve 84 areimmediately operated, and approximately 1 L of the 80° C. highconcentration ozone gas stored in the cylinder 87 is blown onto thesurface of the wafer within a 5 second period, then almost all of theresist is stripped away. On completion of this ozone gas emission, thewafer is set at an intermediate rotational speed of 500 rpm, andpropylene carbonate from the vessel 49 is discharged for approximately 5seconds to perform a primary rinse. Following rinsing, the rotation andliquid discharge are once again halted, and the remaining 1 L of highconcentration ozone gas in the cylinder is blown onto the surface of thewafer within a 5 second period, completing the stripping process. Asecondary spin rinse is then performed in the same manner as the primaryrinse. Following completion of this rinse, the hood is raised, and withthe lid 76 in an open state, a stream of high pressure nitrogen gas isdirected at the center of the wafer, while spin drying is performed atapproximately 2500 rpm. When the surface of the wafer has dried, thewafer is removed from the chamber and subjected to a final pure waterrinse and dry using a separate rinser/drier, in a similar manner to theprevious example. The results with the test sample showed that muchquicker stripping was possible with this type of wafer spin treatmentthan had been possible with immersion treatment at 80° C. The quantityof residual organic carbon on the wafer surface was 1.5×10¹³ atoms/cm².

[0123] [Example 8]

[0124] In the dry etching of aluminum films, Cl or Br based gases areused. In such cases, residual amounts of these corrosive gases remainwithin the decomposed films of the resist surface and the side walls ofthe processed sections, and even ashing is unable to remove theseresidual gases. As a result, a subsequent wet treatment is required. Ifthe present invention is applied to this type of treatment sample, thenin order to avoid the danger of aluminum corrosion by residual halogens,treatment should preferably be conducted at as low a temperature aspossible. Consequently, an example is presented for the stripping of aresist with room temperature propylene carbonate containing added ozone.As shown in the example 3 above, the stripping rate for a novolak resistwhich has undergone only post baking is an extremely fast 10 μm/minuteat room temperature. Consequently, it was surmised that the stripping ofa dry etched sample should also be possible within a short time frame,and stripping was attempted using a single substrate spin treatmentmethod, using the modified apparatus of the example 6 which was furthermodified to enable the use of an ozone containing treatment liquid. FIG.4 shows these additional modifications. Those sections not shown in FIG.4 are identical with those of FIG. 2, and the operation of thosesections is as described in the example 5.

[0125] The treatment liquid nozzle 52 is connected directly to a quartzglass ozone saturation vessel 90 with an internal capacity ofapproximately 1.5 L, via an inlet pipe 89. This vessel is attached tothe unmodified treatment liquid supply pipe 51, a gas inlet pipe 91 forsupplying gas to an internal ozone gas diffuser 62, and an internalpressure adjustment pipe 92 which performs the functions of an exhaustpipe and a pressurizing gas inlet pipe. Ozone gas is supplied through apipe 93 from a generation device, via a valve 94. Gas which is bubbledthrough the liquid is exhausted through a three way valve 95. Thestripping treatment is performed by operating a reduced pressure valve97 and the three way valve 95 and supplying high pressure nitrogen gasto the vessel through a pipe 96, thereby forcing ozone saturatedpropylene carbonate through the nozzle 52 for a predetermined period oftime.

[0126] Instead of the ozone gas nozzle used in the aforementionedexample 6, a rinse nozzle 98 for spraying fresh propylene carbonateliquid is provided in parallel with the nozzle 52. The rinse liquid issupplied to the nozzle 98 through a rinse liquid supply pipe 99connected to the vessel 49, having passed through a fine particle filterF under the action of a liquid transport pump P.

[0127] In this example, a novolak resin based positive resist on analuminum film which had been subjected to dry etching with a Cl basedreactive gas, which represents a resist which would typically be removedby ashing, was used as a test system, and a TEG wafer with a patternsimilar to an actual device pattern formed thereon was prepared as atest sample. The thickness of the resist film was 1.2 μm.

[0128] 1 L of room temperature propylene carbonate was placed in thevessel 90, and the liquid was aerated with high concentration ozone gasat flow rate of 2 L/minute for a period of 5 minutes. The three wayvalve 95 was then operated, and under the gas pressure of nitrogen gas,ozone saturated propylene carbonate was sprayed onto the wafer for 30seconds at a flow rate of 120 mL/minute. Propylene carbonate from thevessel 49 was then supplied to the nozzle 98 by the liquid transportpump P, and a 5 second rinse was performed at the same flow rate.Subsequent treatment was performed in the same manner as the example 6,and following rinsing in ultra pure water and drying, the wafer surfacewas inspected under an electron microscope. No residual resist wasvisible, even on the side walls of the processed sections.

[0129] [Example 9]

[0130] This example presents applications of the present invention topaint film stripping from a steel plate component painted with anacrylic based synthetic resin paint, and to oil film removal from amachined component covered in an oil film of a cutting oil.

[0131] (9-1) Ethylene carbonate liquid at 80° C. was placed in astainless steel vessel provided with a megasonic diaphragm in the baseand a heater on the side walls, and a steel plate component painted withan acrylic based synthetic resin paint was immersed in the liquid andsubjected to ultrasonic agitation at 1 MHz. The majority of the paintfilm had been stripped within 10 minutes, and a simple water shower wassufficient for final cleaning. The ethylene carbonate liquid followingtreatment was colored due to the paint pigment, but bubbling highconcentration ozone gas through the liquid for 5 minutes at a rate of 2L/minute produced a marked discoloration of the liquid.

[0132] (9-2) Ethylene carbonate liquid was placed in a stainless steelvessel equipped with a heater, and following heating to 100° C., amachined component covered in an oil film of cutting oil was immersed inthe liquid for 2 minutes. The cutting oil dissolved in the liquid,enabling the oil film to be removed. The treatment liquid was coloredslightly yellow, but bubbling ozone gas through the liquid in the samemanner as described above resulted in total elimination of the coloringin approximately 5 minutes.

[0133] [Example 10]

[0134] The example 4 showed that a 1×10¹⁴ ions/cm² ion implantationhardened resist could be stripped using heated ethylene carbonate,although on completion of the stripping process, fine particles of thehardened resist remain dispersed within the liquid. If repeatedstripping treatments are conducted with the same liquid, then thequantity of these dispersed particles gradually increases, and soadhesion to the stripped surface becomes more likely, and removal byrinsing becomes more difficult. Consequently, if the temperature of theethylene carbonate liquid is lowered to approximately 40° C. and highconcentration ozone gas is bubbled through the liquid, then within 1 to2 minutes these fine particles decompose and are dissolved in theliquid, forming a uniform liquid phase. As a result, the treatmentliquid can be circulated and reused without placing a heavy load on thefine particle filter.

[0135]FIG. 5 is a schematic diagram showing a batch treatment systemdesigned to apply these modifications. In this system, a draft and arobot for moving the wafers 4 similar to those described in FIG. 1 arerequired, although because these components are completely standarditems, their description here is omitted. However, in the system shown acassette is not used for movement of the wafers, but rather a waferchuck (not shown in the diagram) is used, which transfers each set ofwafers sequentially to wafer cradles 103, 104, 105 provided within astripping vessel 100, a treatment liquid rinse vessel 101 and an ultrapure water rinse vessel 102 respectively. In this system, 8 six inchwafers are aligned vertically with a spacing of 6 mm between wafers, andthese wafers are treated in approximately 3 L of liquid. A heater 12capable of heating the ethylene carbonate liquid to a temperature of150° C. is provided within the stripping vessel 100, and a similarheater 12′ is also provided in the treatment liquid rinse vessel 101,for maintaining the approximately 3 L of ethylene carbonate liquidcontained therein at a temperature of approximately 40° C. Freshethylene carbonate liquid is heated and maintained at approximately 40°C. within a liquid storage vessel (not shown in the diagram), and issupplied to the vessel 101 through a rinse treatment liquid supply pipe21 (hereafter, piping for liquids is shown using solid bold lines) via avalve 20, and is also transferred to a small capacity ozone removalvessel 106 through a connection pipe 107. Once these vessels are full,the liquid overflows through a connection pipe 108, filling thestripping vessel, and when approximately 3 L of liquid has flowed intothe vessel, the valve 20 is closed, and the treatment liquid preparationphase is complete. At the base of the vessel 106 are provided a heater12 for maintaining the temperature, and a diffuser 109 which is used forbubbling high purity nitrogen gas through the liquid to remove dissolvedozone, and which is connected to a nitrogen inlet pipe 111 (hereafter,piping for gases is shown using dashed bold lines) via a valve 110. Anozone gas diffuser 11 provided above the heater 12′ within the vessel101 is connected to an ozone gas inlet pipe 14 via a valve 13. Althoughno piping is shown in the diagram, the ultra pure water rinse vessel 102is of an overflow type construction, and contains a wafer cradle 105provided with sufficient wafer slots to accommodate three treatmentbatches, namely 24 wafers, so as to best conform with a conventionalbatch treatment system, wherein the drying process following pure waterrinsing is typically conducted in batches of 24 or 25 wafers. The vessel102 is an elongated shape, containing additional wafer cradles 105′,105″ arranged in parallel, and during the rinsing process the wafers aretransferred to the next cradle every 6 minutes, without being removedfrom the water, and are then finally supplied to a batch spin drier.Dams 112, which are raised only during movement of the wafers, are alsoprovided between the cradles in the vessel 102.

[0136] Using the system described above, 1×10¹⁴ ions/cm²B⁺ ionimplantation hardened resist wafers from the example 4 were used as testsamples. The liquid in the vessel 100 was set to a temperature of 80°C., the liquid in the vessel 101 was set to 40° C., and highconcentration ozone gas was then bubbled through the liquid in thevessel 101 at a flow rate of 2 L/minute. At the same time, nitrogenaeration of the vessel 106 was also commenced. Following 5 minutes ofozone gas aeration, 8 wafers were immersed in the vessel 100 for 1minute, subsequently raised out of the liquid, and once dripping of theliquid had stopped, the wafers were set inside the vessel 101 and rinsedin ozone containing ethylene carbonate liquid for 1 minute (during thisperiod, any dissolved resist or fine particles of hardened resistcarried across with the wafers were decomposed), before being raised outof the vessel 101 in a similar manner to the removal from the vessel100, and transferred to the overflowing pure water in the vessel 102.Using 8 wafers for each stripping lot, this stripping and rinsingtreatment was repeated, and once the cradle 105 was filled with 24wafers, the rinsing and drying process was conducted in the mannerdescribed above.

[0137] Naked eye inspection of each of these 24 wafers reveled that theresists had been completely removed. In addition, a sample of the waferswere also inspected under a microscope, and confirmed that the resisthad been effectively stripped, with no fine particles of hardened resistvisible. A further two wafer samples were subjected to charged particleradioactivation analysis to determine the quantity of residual organiccarbon on the surface, and yielded results of (1.8 and 2.9)×10¹³atoms/cm², indicating that this ion implantation hardened resist hadbeen satisfactorily stripped within a very short time of only oneminute. Accordingly, hardened resists produced following dry etching canalso be stripped within a short time period.

[0138] [Example 11]

[0139] Using the apparatus and treatment method described in the example10, 1×10¹⁵ ions/cm²B⁺ ion implantation hardened resist wafers from theexample 4 were used, as is (that is, without prior treatment with adiamond dicer) in a stripping test. However, the temperature of theethylene carbonate liquid in the vessel 100 was raised to 150° C., andthe immersion time was increased to 2 minutes. The test was conductedwith only two wafers, and following drying, these wafers were subjectedto the same observations as described in the previous example. Thestripping was satisfactory, and no fine particles of hardened resistwere visible. Determination of the quantity of residual organic carbonusing charged particle radioactivation analysis yielded results of (2.5and 3.6) ×10¹³ atoms/cm², which while being slightly higher than theprevious results, still represent a satisfactory level of cleanliness.

[0140] [Example 12]

[0141] An example based on the stripping apparatus of the example 10,but also provided with a mechanism for an ethylene carbonate recyclingsystem using ozone treatment, similar to the system shown in FIG. 2 ofthe example 5, is presented in FIG. 5. In this recycling system, theconstruction of the gas treatment vessel 56 and the recycled liquidvessel 67 are almost identical with that shown in FIG. 2, and therespective capacity of these vessels must be at least the capacity ofthe vessel 100 in the case of the gas treatment vessel 56, and at leasttwice that capacity in the case of the recycled liquid vessel 67. Thevessel 67 contains approximately 4 L of ethylene carbonate liquid whichhas been previously transferred from the liquid storage tank via a valve113 and a liquid supply pipe 114, and this liquid is heated andmaintained at 80° C.

[0142] In the same manner as the example 10, once the treatment liquidhas treated 6 lots of 8 wafers, a valve 37 is opened, and the liquid iscooled to approximately 40° C. through the action of a waste liquidcooler 54 and transferred to the vessel 56. Heated liquid from thevessel 67 is supplied to the empty vessel 100 through a liquid transportpump P and a fluororesin precision filter F, and at the same time, thevalve 20 is opened and approximately 200 mL of fresh ethylene carbonateliquid is added to the vessel 101. The liquid in the vessel 100, whichwill have increased in volume with the movement of liquid from the ozonedegassed vessel 106, is then adjusted to a temperature of 80° C. usingthe heater 12. Subsequently 6 lots, each containing 8 wafers with thesame specifications as those of the example 10, were treated in the samemanner as above. The ethylene carbonate liquid inside the vessel 56 ismaintained at approximately 40° C., and high concentration ozone gas isthen bubbled through the liquid for 5 minutes at a flow rate of 2L/minute. This treatment causes decomposition of the dissolved resist,and the liquid changes from a deep brown color to a transparent paleblue. Any fine particles of hardened resist are also decomposed andeliminated. High purity nitrogen gas is then bubbled through the liquidfor one minute at the same flow rate to remove the ozone, and the liquidis then transferred to the vessel 67 by a liquid transport pump. Theliquid in the vessel 67 is then heated to 80° C. within a 5 minuteperiod. When 6 treatment lots of 8 wafers have been completed in thevessel 100, the treatment liquid is transferred to the vessel 56 in thesame manner as described above, and 3 L of liquid at 80° C. is pumpedfrom the vessel 67 into the vessel 100. This sequence of processes isthen repeated. When 16 occurrences of the 6 treatment lots of 8 wafershave been completed, that is after the treatment of 768 wafers, theapproximately 7 L of liquid in the vessel 67 and the approximately 3 Lof liquid in the vessel 56 is discharged to waste. Pure ethylenecarbonate liquid can be efficiently recovered from this waste liquid byvacuum distillation.

[0143] The final 8 wafers subjected to stripping were subjected to bothnaked eye inspection and determination of the residual organic carbon onthe surface using charged particle radioactivation analysis, any therewere no significant differences from the results of the example 10,indicating satisfactory stripping. Accordingly, using this series oftreatments, each 1 L of ethylene carbonate liquid was able to be usedfor stripping 77 wafers. In contrast, in conventional organic solventtreatments, 3 L of solvent is required for stripping 8 wafers×6 lots=48wafers, or in other words, a stripping performance of 16 wafers per 1 Lof liquid. Consequently, the quantity of stripping treatment liquidrequired in this example is approximately ⅕th that of conventionaltreatments.

[0144] [Example 13]

[0145] Although semiconductor resists are increasing in purity, theystill contain large amounts of impurities when compared with ultra highpurity chemicals used for cleaning. Consequently, if the number of timesthat a stripping liquid is used for treatment is increased five foldover conventional treatments, as in the previous example, then in thefinal stripping treatment process, the concentration of impurities inthe liquid will have risen to 5 times that of a conventional treatmentliquid, increasing the danger of contamination of the stripped surfacewith impurities. In order to investigate how impurities within ethylenecarbonate liquid adhere to a stripped surface, a radiochemical tracermethod was employed with a Si device, using labeling with theradioactive isotope ⁵⁹Fe of Fe, which represents one of the most harmfulheavy metals. As a result, it was discovered that an Fe concentration of50 ppb in the liquid lead to Fe contamination of (2.7 to 6.6)×10¹⁰atoms/cm² on the silicon surface, and (8 to 21) ×10¹⁰ atoms/cm² on anoxide film. In order to reduce this contamination to a level of not morethan 10⁹ atoms/cm², the Fe concentration within the ethylene carbonateliquid must be restricted to not more than 1 ppb and 0.5 ppbrespectively. If a resist film contains Fe impurities at a level of 1ppm, then in the previous example in which 768 wafers were treated, Feimpurities would total 20 μg, and if this quantity of Fe exists within10 L of liquid, then the Fe concentration derived from the resist willtotal 2 ppb. Accordingly, the calculated quantity of Fe permitted withina resist is 250 ppb.

[0146] However, if the ultra pure water rinse following stripping isperformed using so-called HF water containing 10 ppm of hydrofluoricacid, then it was found by tracer methods using radioactive isotopelabeling that the quantity of adhered contaminants such as Fe, Na, Crand Ni could be reduced by at least one power of ten. In such a case,impurities of even several ppm in the resist film cease to be a problem.

[0147] In contrast, when stripping treatment was attempted with 1% of acarboxylic acid based chelating agent added to the ethylene carbonateliquid or the propylene carbonate, it was evident that in both cases,contamination arising from heavy metal impurities adhering to a siliconsurface or an oxide film surface was far less likely. When 50 ppb of⁵⁹Fe labeled Fe was added to ethylene carbonate liquid, and then 1% byweight of tartaric acid was added to the liquid before the liquid wasused in a stripping treatment, a similar stripping rate was achieved toa liquid sample containing no added tartaric acid. However, in the caseof the tartaric acid containing liquid, tracer methods similar to thosedescribed above revealed that the degree of contamination of a strippedoxide film surface due to adhered Fe was only 8×10⁸ atoms/cm².Similarly, when 50 ppb of ⁵⁷Ni labeled Ni was added to propylenecarbonate, and then 1% by weight of citric acid was added to the liquidbefore the liquid was used in a stripping treatment, once again therewas no effect on the stripping rate, and the degree of contamination ofa stripped oxide film surface due to adhered Ni was only 2×10⁸atoms/cm². Reducing the effects of contamination of the strippingtreatment liquid by using this type of chelate addition is an effectiveoption. The carboxylic acid based chelating agents used in suchtreatment are comparatively unreactive with respect to ozone dissolvedin the alkylene carbonate liquid, and as such are not a significantimpediment to the repeated use of the stripping liquid.

[0148] [Example 14]

[0149] The widely used batch treatment based multiple tank immersionmethod comprises a plurality of chemical treatment vessels and a purewater vessel, and the first chemical vessel is usually heated. In thisexample, treatment was performed with as few alterations as possible tothis type of conventional method. A mixed treatment liquid of ethylenecarbonate and propylene carbonate according to the present invention wasapplied to a process for stripping a residual resist film left afterashing with an organic solvent. Because the target for removal was aresist from which the hardened degenerated sections had already beenremoved, heating the mixed treatment liquid to a temperature of 50 to60° C. enabled stripping to be completed with ease, and direct rinsingwith water also produced no problems. Consequently, a stripping systemshown in FIG. 6 was used, using the transport system of the example 10,and with the stripping treatment tact time set to 2 minutes, andotherwise similar to the configuration shown in FIG. 5 with a heatedtreatment vessel 100 for stripping and a pure water rinse vessel 102.Batch treatment was performed on 25 six inch wafers per lot, and 8 L ofliquid in the vessel 100 was sufficient for the treatment.

[0150] In this example, as was the case above, the stripping liquid inthe vessel 100 is changed after treatment of 6 lots, that is every 12minutes, and consideration was given to the case in which there isinsufficient space around the stripping apparatus to enable installationof a mechanism for the decomposition and recycling treatment of thisdischarged liquid by ozone gas, so that as is shown schematically inFIG. 6, the recycling treatment is performed in a separate location, andperhaps a separate building, from the stripping apparatus.

[0151] A mixture of equivalent quantities of ethylene carbonate andpropylene carbonate was used as the treatment liquid, although it can beestimated from Table 1 of the example 3 that unless propylene carbonate,which is a liquid even at temperatures below 0° C., is cooled to atemperature below room temperature, then there is no significantreduction in the reaction with ozone. The equivalent mixture is a veryusable liquid at room temperature, and on aeration of the mixture withozone gas at room temperature, reaction with ozone was comparativelyweak. If the temperature at which ozone aeration occurs is lowered, thenthe decomposition effect on the resist weakens, although in this casethe treatment target is not a hardened resist, and so satisfactorydecomposition can be achieved at lower temperatures, and recycling ofthe mixed liquid is also possible.

[0152] Liquid supply tanks 115, 115′ and waste liquid stock tanks 116,116′ each have a capacity of 100 L, and are of identical shape andfitted with casters 117. Initially, the tanks 115, 115′ are both filledwith fresh treatment liquid, and first, a liquid removal pipe 119 forthe tank 115, which is fitted with a valve 118, is connected to thetreatment liquid supply pipe 51 of the stripping apparatus. Then, theaction of a liquid transport pump P can be used to pump 8 L of treatmentliquid through a precision filter F and a water heater 120 and into thevessel 100.

[0153] The temperature of the liquid in the vessel 100 is maintained at50 to 60° C. by the heater 12, and treatment is performed on 6 lots. Thetank 116 is initially empty, and a liquid inlet pipe 122 fitted with avalve 121 is connected to the liquid waste pipe 36 of the vessel 100.Following completion of the treatment, the valves 37, 121 are opened andthe treatment liquid is discharged into the tank 116. During thisdischarge process, the cooler 54 cools the liquid down to roomtemperature. Following the completion of ten 6 lot treatments in 2hours, the tanks 115 and 116 are exchanged with the tanks 115′ and 116′respectively, and lot treatment continues.

[0154] The tanks 115, 116 are then transported to the location of theozone treatment apparatus. The ozone treatment apparatus is based arounda gas treatment vessel 56 (with a treatment liquid capacity of 5 L)equipped with a gas diffuser 62 which is connected to an ozone gasgeneration device (not shown in the diagram) via a valve 61, and to ahigh pressure nitrogen pipe via a valve 63. Expended gas is transferredto a waste gas treatment facility (not shown in the diagram) via anexhaust gas outlet 123. The liquid removal pipe 119 of the tank 116 isconnected to the liquid inlet pipe 124 of the vessel 56, and a liquidremoval pipe 125 of the vessel 56 is connected to the liquid inlet pipe122 of the tank 115, and by operating the valves 118, 126 and a liquidtransport pump P, liquid is transferred from the tank 116 to the vessel56. By opening and closing the valves 60, 61, and 63, first ozone gas ofconcentration 210 mg/L is bubbled through the liquid for 5 minutes at aflow rate of 4 L/minute, and then nitrogen gas is bubbled through theliquid for one minute at the same flow rate. The resist is totallydecomposed, and the liquid changes to a transparent pale blue color. Atthis point, the valves 127, 121 and a liquid transport pump P are usedto transfer the liquid in the vessel 56 to the tank 115. This process isrepeated automatically until the tank 116 is empty. Following thecompletion of ten 6 lot treatments in the stripping vessel 100, thenearly full tank 115 and the empty tank 116 are moved, and exchangedwith the tanks 115′ and 116′ connected to the stripping apparatus. Theremoved tanks are transported to, and connected to the ozone treatmentapparatus, and the process described above is repeated. If the treatmentliquid is discharged from both tanks and replaced with fresh liquidafter completion of 14 cycles of tank treatment, then this equates tothe treatment of 105 wafers with every 1 L of treatment liquid. Incomparison with a conventional treatment in which the treatment liquidis discharged and replaced after 6 lots, which equates with slightlyunder 19 wafers per 1 L of treatment liquid, the quantity of treatmentliquid required in this example is approximately 1/5.5, providing arecycling effect of a similar level to the example 12.

[0155] [Example 15]

[0156] The fact that ethylene carbonate is not classified as a hazardousmaterial under the Fire Services Act is an advantage, although at roomtemperature it is a solid, and can be difficult to use in somesituations, and consequently, the addition of secondary constituentswhich enable stripping to be performed at room temperature wereinvestigated. The mixed treatment liquid with propylene carbonatedescribed in the previous example is perhaps the most effective.However, using such a mixed liquid results in an increased cost forchemicals, and in addition, the recovery of the waste liquid bydistillation becomes more difficult. In cases in which room temperaturetreatment is desirable even if the stripping rate falls to 2 to 3μm/minute, mixtures with water can be considered. To ensure a liquid at25° C., the proportion of water in such a mixture needs to be at least20% by weight. Using a resist coated sample with the same specificationsas those described in the example 1, ozone addition treatment similar tothat described in the example 1 was conducted at 25° C. using ethylenecarbonate liquid containing 20% by weight of water. The stripping wassatisfactory, and a stripping rate of 4 μm/minute was achieved. When theproportion of water in the mixture was increased to 25% by weight andthe temperature was lowered to 20° C. a stripping rate of 2 μm/minutewas achieved, although charged particle radioactivation analysisrevealed that the quantity of organic carbon on the surface hadincreased to approximately 5×10¹³ atoms/cm².

[0157] If 20% by weight of acetic acid is added to ethylene carbonatethen the mixture is a liquid at 25° C., although it solidifies at 20° C.In addition, the flash point also increases significantly, and it can besurmised that such a mixture would not be classified as a hazardousmaterial under the Fire Services Act. Using this composition, astripping test using ozone addition was conducted at 25° C. in the samemanner as that described above. The stripping was satisfactory, and thestripping rate was 10 μm/minute, enabling superior results toconventional immersion treatment in ozone/acetic acid to be achieved.

[0158] [Example 16]

[0159] In the single substrate spin treatment apparatus of the example5, the nozzle 52 for supplying ethylene carbonate treatment liquid ontothe wafer 4′ was exchanged with a commercially available 950 KHzultrasonic spot shower oscillator. In other words, the apparatus wasmodified so that the discharge of liquid from the nozzle attached to themegasonic oscillator sprayed vertically onto the wafer surface, thedistance from the tip of the nozzle to the wafer was 10 mm, and thenozzle itself was able to move across the wafer in an arc from thecenter of the wafer to the edge of the wafer and back. FIG. 7 is anoverhead view showing a trace of the movement of the megasonicoscillator. An oscillator 128 is positioned above a wafer 4′ and isconnected, via a connection pipe 130, to a rotational axis 129 with thesame function as the rotatable supply pipe 78 of the example 7 shown inFIG. 3. A nozzle 132 which moves back and forth along an arc trace 131supplies treatment liquid onto the wafer 4′.

[0160] Using a dry etched novolak resist sample from the example 5, thesame 100° C. high purity ethylene carbonate liquid was supplied to thewafer surface under conditions including a rotational speed of 200 rpm,a treatment time of 8 seconds, a flow rate of 1 L/minute, and withmegasonic irradiation. During this 8 second treatment period theoscillator was moved so that the nozzle moved back and forth along thedesignated trajectory, completing one movement cycle across the waferand back every 2 seconds. The wafer rotational speed was then increasedto 1000 rpm, and the same process repeated for a further 2 seconds, andthen subsequent treatment was performed in the same manner as theexample 5. Inspection of the sample surface under an electron microscoperevealed that the resist had been completely removed. The stripping ratefor the resist was approximately twice the rate observed when nomegasonic irradiation was used. The vapor pressure of ethylene carbonateat 100° C. is 8 mmHg, meaning high frequency ultrasonic processing usinga spot shower can be performed at high temperatures.

[0161] [Example 17]

[0162] When ethylene carbonate was used for stripping a resist on ametal wiring film, determination of the degree of damage caused to themetal surface was tried based on the elution rate of the metal into theliquid. First, 500 g of high purity ethylene carbonate liquid carefullypurified by distillation was placed in a dish of high purity quartzglass, forming a depth of liquid of approximately 10 mm, and thetemperature of the liquid was maintained at 120° C. Next, a samplecomprising a film of Al of thickness 1000 Å formed on an eight inchsilicon wafer was immersed in the liquid in the dish, with the metalsurface facing upward. After immersion for 10 minutes, a portion of theliquid was withdrawn and subjected to ICP mass spectrometry to determinethe quantity of eluted Al. The surface of the metal following treatmentwas also inspected under a microscope, but no pit shaped regions oflocalized corrosion were visible, indicating that any elution wasprobably occurring reasonably uniformly across the entire surface. Onthis assumption, the average elution rate was determined, but the resultwas less than the detection limit of 0.03 Å/minute. Using the sameprocedure, it was determined that the elution rate for Cu was less than0.01 Å/minute, and the elution rate for W was 0.035 Å/minute.Accordingly, for those metals which are easily damaged by heat treatmentwith conventional organic solvents, high temperature treatment withethylene carbonate poses no problems whatsoever.

[0163] According to the present invention, by using a treatment liquidformed from liquid ethylene carbonate and/or propylene carbonate, and inparticular such a treatment liquid containing dissolved ozone gas,organic films on substrate surfaces, such as dry etched resist films andthe like which have conventionally required ashing, can be effectivelyremoved in an extremely short period of time. A treatment liquidaccording to the present invention displays a high boiling point and ahigh flash point, and can consequently be applied to treatment underhigh temperature conditions, producing a considerable improvement instripping performance. Furthermore, a treatment liquid of the presentinvention is also very safe, and suffers from little environmentalproblems. Of particular importance is the fact that this resist removaltreatment has no deleterious effects on easily damaged metal substratefilms such as Al, Cu or W. In addition, following treatment the liquidcan be easily recycled by aerating with ozone gas, enabling reuse of theliquid, which offers obvious economic benefits. Furthermore, if atreatment liquid containing an added carboxylic acid complexing agent isused, then the contamination of a silicon surface with adhered metalimpurities can also be prevented.

What is claimed is:
 1. A method for removing an organic film on asurface of a substrate, comprising: bringing a treatment liquidcomprising liquid ethylene carbonate, propylene carbonate, or both ofthem into contact with said substrate to remove said organic film,thereby allowing material constituting said organic film to migrate intosaid treatment liquid, decomposing said material in said treatmentliquid into low molecular weight material by ozone, thereby said ozonetreated treatment liquid being regenerated as a treatment liquid, andrecycling the treatment liquid thus regenerated for treating anothersubstrate.
 2. The method according to claim 1, wherein said treatmentliquid comprises liquid ethylene carbonate, and during said contactingwith said substrate said treatment liquid has a temperature within arange from 40 to 200° C.
 3. The method according to claim 1, whereinsaid treatment liquid comprises propylene carbonate or both of ethylenecarbonate and propylene carbonate, and during said contacting with saidsubstrate said treatment liquid has a temperature within a range from 20to 200° C.
 4. The method according to claim 1, wherein the contacting ofsaid treatment liquid with said substrate surface is effected byimmersing said substrate with an organic film in said treatment liquid.5. The method according claim 1, wherein the contacting of saidtreatment liquid with said substrate surface is effected by supplyingsaid treatment liquid from a nozzle onto said substrate surface, andforming and then moving a liquid film of said liquid.
 6. The methodaccording claim 1, wherein the contacting of said treatment liquid withsaid substrate surface is effected by forming a liquid film of saidtreatment liquid on said substrate surface in an atmosphere of a gascontaining a high concentration of ozone, and then moving said liquidfilm by either continuously or intermittently supplying fresh treatmentliquid to said liquid film.
 7. The method according to claim 1, whichfurther comprises, after said contacting of said substrate and saidtreatment liquid, a step of rinsing said substrate either with ethylenecarbonate liquid at a liquid temperature of 37 to 60° C. containingdissolved ozone, or with propylene carbonate or a mixed liquid ofethylene carbonate and propylene carbonate at a liquid temperature of 20to 50° C. containing dissolved ozone.
 8. The method according to claim1, said step of decomposing the material which has migrated into saidtreatment liquid, is carried out at a different area from an area wheresaid organic film removal treatment has been performed.
 9. The methodaccording to claim 1, wherein during contacting of said treatment liquidwith said substrate surface, high frequency ultrasound is irradiatedthrough said treatment liquid.
 10. The method according to any one ofclaim 1, wherein said organic film is a resist film.
 11. The methodaccording to any one of claim 1, wherein said treatment liquid furthercomprises 0.01 to 2% by weight of an aliphatic carboxylic acid-basedcomplexing agent.
 12. The method according to claim 11, wherein saidaliphatic carboxylic acid based-complexing agent is at least onecompound selected from the group consisting of citric acid, oxalic acidand tartaric acid.
 13. A method for removing an organic film on asurface of a substrate, comprising: bringing a treatment liquidcontaining ozone dissolved in a liquid comprising ethylene carbonate,propylene carbonate, or both of them into contact with said substratewith an organic film on a surface thereof to remove said organic film,wherein said organic film is dissolved said treatment liquid anddecomposed into low molecular weight material, and using the treatmentliquid after removal of said organic film for treating anothersubstrate.
 14. The method according to claim 13, wherein said treatmentliquid after removal of said organic film is recycled as a treatmentliquid as it is for treating another substrate.
 15. The method accordingto claim 13, wherein said treatment liquid after removal of said organicfilm is further subjected to treatment with ozone, and then recycled asa treatment liquid for treating another substrate.
 16. The methodaccording to claim 15, said treatment with ozone is carried out at adifferent area from an area where said ozone-containing treatment liquidis brought into contact with said substrate.
 17. The method according toclaim 13, wherein said treatment liquid containing ozone is prepared bybringing a high concentration ozone-containing gas into contact withsaid liquid comprising ethylene carbonate, propylene carbonate, or bothof them, wherein a distribution coefficient for a relationship between aconcentration of ozone dissolved in said treatment liquid, and aconcentration of ozone in said ozone containing gas is within a rangefrom 0.05 to 0.4.
 18. The method according to claim 13, wherein thecontacting of said ozone-containing treatment liquid with said substratesurface is effected by immersing said substrate with an organic film insaid treatment liquid.
 19. The method according claim 13, wherein thecontacting of said ozone-containing treatment liquid with said substratesurface is effected by supplying said ozone-containing treatment liquidfrom a nozzle onto said substrate surface, and forming and then moving aliquid film of said ozone-containing liquid.
 20. The method accordingclaim 13, wherein the contacting of said ozone-containing treatmentliquid with said substrate surface is effected by forming a liquid filmof said ozone-containing treatment liquid on said substrate surface inan atmosphere of a gas containing a high concentration of ozone, andthen moving said liquid film by either continuously or intermittentlysupplying fresh ozone-containing treatment liquid to said liquid film.21. The method according to claim 13, wherein during contacting of saidtreatment liquid with said substrate surface, high frequency ultrasoundis irradiated through said treatment liquid.
 22. The method according toclaim 13, wherein said organic film is a resist film.
 23. The methodaccording to claim 13, wherein said treatment liquid further comprises0.01 to 2% by weight of an aliphatic carboxylic acid-based complexingagent.
 24. The method according to claim 23, wherein said aliphaticcarboxylic acid based-complexing agent is at least one compound selectedfrom the group consisting of citric acid, oxalic acid and tartaric acid.25. An apparatus for removing an organic film from a surface of asubstrate comprising: (A) a treatment liquid delivery means fortransporting a treatment liquid comprising liquid ethylene carbonate,propylene carbonate, or both thereof to a treatment area, (B) a filmcontact means for bringing said treatment liquid into contact with thesurface of said organic film of said substrate within said treatmentarea, (C) a treatment liquid circulation means for recycling thetreatment liquid used and discharged from said treatment area back tosaid treatment area via one or more temporary storage means, and (D) anozone-containing gas contact means for bringing an ozone-containing gasinto contact with said treatment liquid discharged from said treatmentarea within said treatment area and/or within at least one of saidtemporary storage means.
 26. The apparatus according to claim 25,wherein at least one means of the means (A) to (D) is provided with aheating means.
 27. The apparatus according to claim 25, wherein saidtreatment area comprises a means for immersing a substrate in atreatment liquid.
 28. The apparatus according to claim 25, wherein saidtreatment area comprises a means for applying a treatment liquid to asubstrate through a nozzle.
 29. The apparatus according to claim 25,wherein said treatment area comprises a means for rotating a substrateabout an axis perpendicular to a surface of said substrate.
 30. Theapparatus according to claim 29, further comprising a nozzle forsupplying liquid ethylene carbonate onto a surface of a substraterotating about said axis to form an ethylene carbonate film on saidsurface, and a nozzle for projecting cold air onto said surface of saidsubstrate for solidifying said ethylene carbonate liquid film.
 31. Theapparatus according to claim 29, further comprising a nozzle forsupplying a treatment liquid onto a surface of a substrate rotatingabout said axis, and a nozzle for projecting a high concentration ozonegas onto said surface of said substrate.
 32. The apparatus according toclaim 25, comprising a means for irradiating high frequency ultrasoundthrough a treatment liquid.
 33. The apparatus according to claim 25,wherein said organic film is a resist film.